Of the many trends apparent in the electronic industry, two noteworthy examples include increased processor speeds and reduced power consumption. The trend toward increased processor speed enables execution of sophisticated and complex calculations at ever increasing speeds. Commensurate with an increased speed is the reduced time available in which digital data may be transmitted and received. The trend toward reduced power consumption facilitates devices operable with battery power or other means having a reduced power supply capacity. Also, low power devices dissipate less heat which further enables a higher component density and yet provide reliable operation.
The limited amount of available space on an integrated circuit often constrains the placement of components, including such circuits as drivers. A driver circuit is used to receive an input signal and provides an output signal on interconnect lines. In many applications, a driver requires connections to multiple power supplies. For example, power supply traces often are not available or are unduly problematic.
For efficiency reasons, the output impedance of a driver should be matched to the load of the interconnect lines. Manufacturing tolerances associated with the production of driver circuits may yield some drivers more closely matched than other drivers. In addition, variations in voltage levels can be problematic in the pursuit of high speed reliable data communications. For example, high voltages may result in very fast slew rates and thus lead to excessive current drain during such rapid swings. Ringing of the output voltage levels following level transitions may further delay the sensing of a level. Temperature changes can also have deleterious effects. For example, excessive operating temperature, such as may result from a suboptimal cooling fan, can degrade driver circuit performance and further limit reliable clock speeds, or lead to processing errors.
What is needed in the art is a driver having low power requirements which is reliably operable at a high data communication rate with compensation for variations in process, voltage and temperature.